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It is desired to measure parameters of 230 V / 115 V, 2 kVA, single-phase transformer. The following wattmeters are available in a laboratory: W1: 250 V, 10 A, Low Power Factor W2: 250 V, 5 A, Low Power Factor W3: 150 V, 10 A, High Power Factor W4: 150 V, 5 A, High Power Factor The wattmeters used in open circuit test and short circuit test of the transformer will respectively be

1. W1 and W2
2. W2 and W4
3. W1 and W4
4. W2 and W3

Correct answer: W2 and W4

Solution

W2 is suitable for the open circuit test due to its lower current rating, which is ideal for measuring low power at high voltage, while W4 is appropriate for the short circuit test as it can handle higher current with a high power factor, ensuring accurate measurement under those conditions.

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